Abstract: Protein dynamics are essential to the catalytic function of enzymes, but their precise role and mechanism by which large-scale protein motions and local dynamic fluctuations are connected to the chemical step are still poorly understood. In this talk, I will discuss the role of protein conformational dynamics on the catalyzed hydride transfer by wild-type dihydrofolate reductase (DHFR) and a "dynamics knockout" mutant as expressed in entropy of activation. In addition, I will highlight its implications on the mechanism of OMP decarboxylase, one of the most proficient enzymes that accelerate the reaction rate by more than 20 orders of magnitude.